The present invention concerns a novel strapping machine, for positioning and securing a binding strap about an object or objects, having a single twisted-belt drive to allow inertia to continue to drive strapping material when power is cut off, to allow placement of moving parts within the strapping machine cabinet and to simplify the strapping machine.
Proper operation of strapping machines requires that a particular strap tension be maintained in various locations within the strapping machine. In the initial loading of strapping material into the strapping machine, a reel of material is attached to the outside of the machine and strap is fed into a preliminary feeding mechanism. The strap is threaded through certain strap guides and is fed into a feed wheel mechanism associated with a drive motor. Tension in the strap is created by pulling the leading end of strapping material from the reel using the drive motor and a feed wheel.
As the strapping material is pulled by the feed wheel and drive motor, strap is unraveled from the reel of strapping material, causing the reel to rotate and build up inertial energy due to its rotation. While the strap is pulled at a constant rate, the strapping reel remains in control, unraveling strap at the required rate. However, when pulling ceases suddenly, for example when power is cut off to the drive motor, the inertial energy built up in the strapping reel causes the reel to continue to rotate and continue to unravel strapping material. When the drive motor ceases to operate, the feed wheel driven by the motor, also stops and strapping material cannot move to the next section of the strapping machine. As a result, strapping material accumulates behind the stopped feed wheel.
The rotation of the strapping material reel continues until the reel is stopped by a brake, or other external force, or friction overcomes inertia and the reel stops naturally. If the reel of strapping material is allowed to rotate until it is stopped by friction, the strapping material continues to unravel and loose strapping material accumulates inside the strapping machine. By the time the wheel is stopped, considerable amounts strapping material may be unreeled and may cause jamming of the strapping machine, loss of time in rewinding material and damage to the strapping machine.
Some prior art machines utilize braking means to stop the strap reel upon the cessation of power to the drive motor. However, the sudden stopping of reels of strapping material with a braking device may also cause problems in the strapping machine. Further, these prior art types of braking systems have been hampered by their mechanical complexity and have generally worked only to stop rotation in the forward direction of strap pull.
U.S. Pat. No. 6,039,286, for Inertial Strap Tensioning Apparatus and Method For Strapping Machine, solved many of the problems of prior art tensioning systems, by providing an inertial tensioning system utilizing the natural tendency of the heavy strap reel to stay in motion once it is put into motion. The inertial tensioning system of the ""286 patent includes a belt and a pulley connected to the reel of strapping material and a second motor shaft, disposed at the rear of a gear motor in one embodiment, connected by a belt to the pulley. When the gear motor ceases operation, due, for example, to a cut off of energy, the reel, which continues to turn due to its inertial energy, causes the pulley and belt to turn thereby rotating the second shaft of the gear motor, which in turn, through the special gearing of the motor, causes the first shaft and, thereby, the feed wheel on the first drive shaft to continue to turn and expel strapping material. By utilizing the inertial energy of the larger strap reel to drive the feed wheel, the tension in the strap is maintained, as there is no sudden cut off of strap pulling force, and therefore, no loops are formed in the strap. Friction, and other natural forces, eventually cause the strap reel to come to a gentle stop; stopping the feed wheel gradually while maintaining the tension in the strap. However, the ""286 patent requires, in one embodiment, the use of a gear motor with dual drive shaft and the inclusion of a pulley and belt to be associated with, and therefore, near the strap reel. In most strapping machines, the strap reel is generally placed outside of the machine housing, for ease of installation of new reels of strap. A belt and pulley system, provided to perform the above described inertia transfer function in the machine of the ""286 patent, is also required and is taught to be adjacent the reel, on the outside of the protective housing of the machine. The belt and pulley system is thereby subjected to the ambient elements outside of the protective housing. Further, the placement of moving machinery on the exterior of the machine cabinet poses a potential hazard to the users of the machine.
It would be preferable to protect the mechanical moving parts of machines within the cabinet of the machine. Further, having moving parts inside of a machine housing increases the safety for workers who come in close contact with the strapping machine. It would also be preferable to have a strapping machine with a simplified motor that does not require dual drive shafts with the concomitant complexity in the gearing of such a motor.
In accordance with the present invention, a strapping machine is provided, having a motor with a drive shaft, driven by external power. A reel of strapping material is attached to the strapping machine to provide material for use in strapping an object or objects. An infeed wheel, engaged with the leading end of the strapping material, for pulling additional strapping material from the reel, is also provided on the strapping machine. The infeed wheel is mounted on the drive shaft of the motor, such that the rotation of the drive shaft by the motor causes strapping material to be pulled from the reel, causing the reel to rotate and naturally causing inertial energy to be stored in the reel. A dispenser pulley is attached to the reel of strapping material and a belt, interconnecting the drive shaft and the pulley, is provided. The pulley and belt are placed within the cabinet of the strapping machine. Upon cessation of external power to the motor, the continued rotation of the reel, due to its inertial energy, is translated to the pulley and belt causing the infeed wheel to continue to rotate and pull strapping material from the reel. In this manner strapping material does not accumulate behind the feed wheel.
In the preferred embodiment of the present invention, the drive shaft of the motor and the axis of rotation of the strapping reel are positioned approximately perpendicular to each other and the pulley is mounted concentrically with the reel. The pulley belt must therefore be twisted such that at one end of the belt loop the belt fits concentrically with the pulley and at the other end the belt loop is placed about the drive shaft of the motor. It is to be understood that the drive shaft of the motor and the axis of rotation of the strapping reel may be placed at any convenient angle to each other such that a single belt, twisted to any workable degree, may be utilized to drive the inertial braking system of the present invention, while maintaining the working elements of the inertial braking system within the cabinet of the strapping machine, without departing from the novel scope of the present invention. Further, implements such as pulley guides or wheels may be attached to the drive shaft of the motor, to assist in holding the belt onto the drive shaft, without departing from the novel scope of the present invention.
In the preferred embodiment of the present invention, the pulley and belt are housed within the frame of the strapping machine to provide protection from ambient conditions for the inertial braking system and to house moving parts for the protection of the user of the device. The motor of the present invention may be of the type having means to reverse the rotation of the drive shaft such that the reel of strapping material may be driven in one direction to remove strap and driven in the reverse direction to collect or rewind strap. It is to be understood that a motor which can be reversed by other means, such as reversing the power flow, may be used without departing from the novel scope of the present invention.
A more detailed explanation of the invention is provided in the following description and claims and is illustrated in the accompanying drawings.